Throughout life, everyone is exposed to varied aggressions, either occasionally or in a multiple and/or extreme way. Cosmetic products that temporarily improve the appearance of the skin by masking the irregularities with an opaque cosmetic film are available. This invention proposes an effective alternative to the use of those masking cosmetic products to prevent and/or treat tired skin.
The skin continuously suffers aggression from numerous extrinsic but also intrinsic factors. The extrinsic factors include ultraviolet radiation (mainly linked to exposure to the sun: sunlight-induced aging), environmental pollution and atmospheric pollution, but also wind, heat, low relative humidity levels, contact with household surfactants and other chemicals, abrasives, smoking, alcohol, drugs, diet, stress, mechanical stress, severe atmospheric conditions and so on. The intrinsic factors include chronological aging and the other biochemical changes in the skin. The following may also be cited: hormonal upheavals, fatigue, acne, obesity, tanning, diets, disease, disorders of the blood microcirculation.
In addition, it is now known that our body depends on cycles: day/night alternation, the succession of the seasons, the menstrual cycle, hormonal upheavals, etc. Chronobiology is the study of the biorhythms that result. The skin, like the other organs of the body, lives in time with our internal clock whose period is about 24 hours. In cosmetology, we are now aware that, in order to enhance the efficacy of care, it is sufficient to program it at the most propitious time of day. Studies have demonstrated that the functions of the skin during the day and at night differ markedly: during the day, the skin protects itself against aggressions; during the night, it renews itself when the risk of aggression is lowest. The internal clocks thus enable the various skin functions to be programmed in accordance with man's needs in his environment while compliance with biological rhythms enables optimization of dermatological and cosmetic treatment and care. In this context, day creams are designed to help the skin defend itself from external aggressions while night creams are designed to promote cell turnover and repair the day's damage (bedc Vol. 11-No 6, p 157-159).
Occasional travelers, businessmen traveling between time zones and shift workers who regularly change their working hours, are all exposed to time shifts (the pathological syndrome associated with travel known as ‘jetlag’) reminiscent of deregulations of biological rhythm. Jetlag is the consequence of a desynchronization of certain organs acting as ‘internal clocks’ and external stimuli derived from the environment, enhanced by fatigue and the stress related to traveling and/or personal organization. Tiredness, drowsiness, reduced physical performance, irritability, concentration difficulties, dehydration and poor digestion: the symptoms may persist for a few days to a few weeks, depending on the degree of jetlag. The skin also reflects those dysfunctions of biological rhythm related to jetlag. Chronobiology and circadian regulatory biology study the nature of the internal clocks and the biochemistry and anatomy of the circadian clocks in higher organisms, particularly man. Finding out how to ‘reset’ those clocks is the fundamental aim of research in that field.
Whether extrinsic or intrinsic, whether jetlag or cutaneous chronobiology involved, those factors induce cosmetically undesirable impairment of the visible appearance, clinical and physical properties and physiological and histological functions of the skin. The skin becomes tired, the biological functions and vital faculties of cutaneous tissues grow weaker over time, and even give rise to visible signs of (premature or non-premature) aging of the skin.
The most noteworthy and patent changes include dryness and the development of fine lines and wrinkles, loss of elasticity, wasting and sagging of the skin, dehydrated skin, loss of firmness, thinning of the skin, loss of uniformity of the complexion, a dull complexion, hyperpigmentation, senile lentigines, red spots, a rough, coarse surface texture and a marbled pigmentation. Dull and impaired hair, hair loss and an unbalanced scalp are also frequent symptoms.
Other less obvious but nonetheless measurable changes occur when the skin ages or is subject to chronic environmental aggression and include a general reduction in the vitality of the tissues and cells, a slowed cell replication, a decrease in protein synthesis, an increase in proteolysis, a decrease in cutaneous blood circulation or vasodilatation with blood stasis, a seepage from the blood compartment, reduced water content, an accumulation of errors in the structure and function of proteins, a deleterious change in the skin's barrier properties, connective tissues and cohesion, and a reduced ability of the skin to remodel and repair itself.
Skin cells, like all the other cells of the body, are the site of bioenergetic metabolic processes. The energy necessary for all cell functions (macromolecule synthesis, multiplication, defense, signaling, etc.) can be derived from ATP, the classic intracellular energy source, or be derived from the exterior. Tired skin, exposed to the external and internal aggressions described above, must thus have the ability to respond quickly by cellular protection and repair mechanisms, for which ‘easy’ chemical energy sources are important.
Providing active support for that requirement of the skin, supplying energy and contributing to the constitution of reserves, may thus be of interest to cosmetology. Nonetheless, ATP is not stable as an active substance in cosmetic preparations.